1. Field
The present disclosure relates to a polymeric film for a non-enzymatic glucose sensor and, more particularly, to a polymeric film and a glucose sensor comprising the polymeric film, in which the number of interactions between the saccharides other than glucose and the non-enzymatic glucose sensor are reduced by the polymeric film, making it possible to improve sensor selectivity to glucose and minimize the interactions between the organic materials and the non-enzymatic glucose filter that would otherwise present obstacles to measurement.
2. Description of the Related Art
Characteristics of diabetes, including hyperglycemia (a defect in insulin secretion and abnormal insulin action levels) and complications thereof (injuries to eyes, kidneys, nerves, the heart, or blood vessels) have come to the forefront nationally and socially, and diabetes has been recognized as being a serious disease. As a result, there is a great deal of effort set forth for preventing and delaying the onset of chronic complications from diabetes. For this reason, it is very important for a selection of a treatment method and prognosis to be able to estimate the suitability of the treatment via continuous observation of blood sugar, and then quickly apply the result thus obtained to a treatment process. Therefore, blood sugar should be closely managed in a patient with diabetes, and rapid examination should be carried out so as to enable quick diagnosis and estimation of a treatment by a medical team. To this end, self-monitored blood sugar measurement has been increased. To achieve this, a study of a self-monitoring sensor and a system of blood sugar measurement is actively in progress.
An electrochemical sensor is the simplest sensor in terms of its signal conversion process, because it converts specific information into an electric signal. An electrochemical sensor does not require a fixed space or an elaborate alignment, unlike those methods that use light; it is not as affected by external vibration as measurements of mass or mechanical changes; and it can be operated with high sensitivity within a very broad range of concentrations. Since the whole of the electrochemical measuring device, as well as a detection part thereof, can be easily miniaturized and integrated at low cost, an electrochemical measuring device is a most preferred industrial means of measurement so long as it exhibits sufficient performance. The downside of electrochemical measurement is insufficient selectivity, and as a result, an electrochemical measuring device should be in contact with a sample. In the case of measuring a human body, this means that measurement should be mostly performed via an invasive inspection.
As the concept of biosensors has developed, new testing methodology has been proposed, in which the selectivity problems of electrochemical sensors can be solved by combining biomaterials with an electrode. As an example, there is an enzyme electrode. Most bio-enzymes selectively bind and react only to a specific substrate. Therefore, selectivity problems may be solved by fixing an enzyme on an electrode, and then indirectly measuring the chemical environment that is changed by the enzyme reaction.
A commercialized enzymatic glucose sensor is based on such a principle, i.e., that of an enzyme electrode. However, the activity of biomaterials in general, and enzymes in particular, are too sensitive to the influences resulting from their structural environments. The activity of a manufactured example is therefore infinitely worse than what would have been initially expected. Even in the case of a glucose sensor according to the most successful manufactured examples, the cost for using an enzyme is overwhelmingly high as compared to a sensor that does not use biomaterials. The causes of increased cost may include quality management during mass production, limitations arising from expiration dates, packaging costs, and oxygen concentration dependence. Using an enzyme increases these costs. Therefore, even though a lot of improvements have been achieved, a fundamental breakthrough in this technology has not yet been revealed. As an alternative way to overcome the disadvantages enzymatic sensors, a study involving a non-enzymatic glucose sensor that uses carbon nanotubes, nanoparticles, Pt, nanoporous Au, a metal-oxide electrode, and the like is in process. However, the selectivity problem of such a non-enzymatic glucose sensor has not been solved, and thus, such a sensor is not being used. It is therefore necessary to develop a new non-enzymatic glucose sensor that solves the disadvantages of conventional enzymatic sensors by using a metal electrode.
An earlier study on non-enzymatic electrochemical oxidation of saccharides focused on the use of generally-used electrode materials, such as C, Cu, Ni, Fe, Pt, and Au (see R. Jin, Y. C. Cao, E. Hao, G. S. Metraux, G. C. Schatz, C. A. Mirkin, Nature 425 (2003) 487; D. Golberg, P. M. F. J. Costa, M. Mitome, S. Hampel, D. Haase, C. Mueller, A. Leonhardt, Y. Bando, Adv. Mater. 19 (2007) 1937). However, these materials cause fundamental problems of, for example, low efficiency and toxicity as a result of a chemically adsorbed intermediate. Therefore, it is necessary to develop an ideal material that is capable of promoting the oxidation of saccharides such as glucose while also overcoming the above-mentioned problems. Thus, metal catalysts are receiving focused attention. Studies on the structures of various types, such as nanoparticles (Au, Pt (see J. O'M. Bochris, S. U. M. Khan, Surface Electrochemistry, Plenum Press, New York, USA, 1993)), a single dendrite (Ag (see A. Gutes, C. Carraro, R. Maboudian, J. Am. Chem. Soc. 132 (2010) 1476), Cu (see S. Sahoo, S. Husale, B. Colwill, T. M. Lu, S. Nayak, P. M. Ajayan, ACS Nano 3 (2009) 3935), Pt (see J. K. Kawasaki, C. B. Arnold, Nano Lett. 11 (2011) 781)), and an alloy dendrite (Pd—Pt (see B. Lim, M. Jiang, P. H. C. Camargo, E. C. Cho, J. Tao, X. Lu, Y. Zhu, Y. Xia, Science 324 (2009) 1302), Pd—Ag (see J. Huang, S. Vongehr, S. Tang, H. Lu, X. Meng, J. Phys. Chem. C 114 (2010) 15005), Pt—Pb (see J. Wang, R. M. Asmussen, B. Adams, D. F. Thomas, A. Chen, Chem. Mater. 21 (2009) 1716), Cu—Co (see H.-B Noh, K.-S. Lee, P. Chandra, M.-S. Won, Y.-B. Shim, Electrochimica Acta 61 (2012) 36)) have been carried out. Among them, the structure of an alloy dendrite has high oxidation catalyst function due to a unique layer structure having very high surface area and several active sites, and thus, is possible for it to be used as a non-enzymatic glucose oxidation catalyst (see K. E. Toghill, R. G. Comton, Int. J. Electrochem. Sci. 5 (2010) 1246)].
In the case of an enzymatic glucose sensor, there is a technical limitation in that variations in properties are present as a result of deteriorations of the enzyme and differences between temperatures and production lots (batch). To overcome this, many studies of non-enzymatic glucose sensors are in progress, but because of the properties thereof, other saccharides and organic materials (ascorbic acid (AA) and acetaminophen (AP)) other than glucose may be oxidized, and thus, there exists a need to solve the selectivity problem of making a sensor that is selective only to glucose.
As one method for solving the issue of such selectivity, a study of a functional film capable of selectively passing glucose is required, and until now, for removing the blocking actions of organic materials (AA, AP), a study on the use of a functional protection film (for example, Nafion®, Kel-F, cellulose acetate, chitosan, poly(ethyleneimine), polyurethane, and the like) to a metal or metal oxide (nanoporous Pt) electrode has been reported. However, until now, a study on a polymeric film for increasing the selectivity of glucose from among various saccharides has not been reported.